Entering a default line item in service order

Hi All,

My requirement is whenever we create a service order a default product ( fetching based on some custom tables) should populate automatically at line item level.

i have checked and the component is BT116IT_SRVO for line items. I know if I have to add the default line item , i need to enhance the component. But I am still confused where to write the code to put the default line item .I am new to crm webui .

Could anybody please help me where to write the code for the same.

Thanks in advance.

Thanks

Piyush